A Fatal Joke
by Kaneki Phantomhive
Summary: When a harmless April Fools' joke on the Shinigami backfires, Ciel Phantomhive's soul, along with his contract with Sebastian, hangs in the balance. Sebastian uses a secret hidden in his twisted past to invoke an ancient trial over the ownership of Ciel Phantomhive's soul. Who will win? And what will happen to Sebastian if he loses? !FallenAngelSebastian!DemonCiel! T for violence.
1. Chapter 1

**Hi to all readers. I appreciate you viewing my story. Second chapter will be up soon. Please read, like and review. Constructive criticism is accepted. I hope you enjoy this chapter.**

 **Disclaimer: Much as I wish it, I did not wake up as Yana Toboso this morning, otherwise why would I be writing fanfiction? On with the story!**

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"I wish for something entertaining, Sebastian. I'm bored." Ciel whined as his demon butler pulled on his stockings. Sebastian smirked, seemingly considering the matter. He looked up at Ciel before replying. "My Lord, I think I know just the thing. It's April Fools tomorrow, yes?" Sebastian clarified. Confused, Ciel stared at him. "I mean, yes, but, um, WHY Sebastian?" Ciel inquired innocently. Sebastian tied Ciel's eye patch round his head, concealing his shining violet eye, hiding the purple pentagram that bound him to his Contract with the demon. Ciel sipped his Earl Grey, while Sebastian elaborated on his cryptic statement. "On April Fools, God and Satan abandon the normal rules of society. These rules don't apply to humans, but to demons. On April Fools, a demon cannot die. However, the Reapers don't know that. And, I got permission from God himself. You, Young Master, are going to meet with Satan tonight. We are going to play one Hell of a joke on those damned Shinigami."

The descent to Hell was noisy. That was all Ciel could think as he tumbled down the deep canyon, held securely in his butler's arms. They had been falling for what seemed like years; how much longer were the going to plummet aimlessly through open space? Ciel wondered. Suddenly, he felt the air whoosh from his chest as Sebastian hit the ground heavily. He looked up. Sebastian straightened and whispered in his ear. "Welcome to Hell, My Lord." Ciel's eyes widened. Before him was a set of huge obsidian gates inset with onyx and rubies, beyond that, towering volcanoes, magma lakes and tall, foreboding palaces completed the scene. "Either side of the gate were two tall figures in long black robes. Switching Ciel's weight in his arms, Sebastian approached the gates and said "I am the Contractor Sebastian Michaelis, and I have a meeting with Satan Lucifer. He is expecting me." Without a word, the strange figures moved aside, and Sebastian carried Ciel through the gates, ever closer to Lucifer's castle.

The pair strode through the dark corridors of Satan's castle before emerging in a huge room that flickered with the dim light of a thousand candles, and in that room was a ginormous black throne. Upon that throne sat the King of demons, the great Satan Lucifer himself. Sebastian set Ciel to the ground and, surprising said Earl immensely, folded his long limbs into an elegant bow. The demon king stared at them imperiously before his stern frown became a grin that showed the tips of his sharp fangs. "Michaelis! Just the demon I wanted to see. Up for playing a trick on the Death Gods, my friend? Don't worry, I've even talked it over with God, and your little contracted soul will be part of it too. So what do you say, eh Michaelis!" The demon snickered, evidently visualizing the effects of his prank on said Reapers. Sebastian seemed to ponder his request before laughing and stating the obvious. "What do you want us to do? I'm curious. Your summoning message didn't give much away." "Simple, Michaelis. Firstly, your precious Young Master is going to be made a demon for the night. The Shinigami will find that little development interesting. And secondly, what's one of the few things that can kill a demon apart from a demon sword? Come on, think Michaelis! What can kill a demon apart from a demon sword?" Sebastian thought for a moment. "Let's see. The only thing that springs to mind is a Death Scythe... wait a minute, Lucifer, you don't mean... " Sebastian looked up with a hopeful grin. "Oh yes I do." Satan confirmed. "I told you, I got permission from God. You will be immune to Death Scythes until midnight on April Fool's. Until then..." And here Satan's face split into a sardonic grin,"Do what you like. But first." He pointed his finger at Ciel, and the small Earl screamed in pain and shone with a dark aura. Ciel's eyes opened, and they were not their normal cerulean blue, but a deep, coppery red. He smiled. "Oh, this is going to be fun Sebastian. Let's go." And, with Lucifer's permission, they left.

Once back in the human realm, Ciel turned to Sebastian. "Where are the Shinigami, and how can we play this to our advantage?" He asked Sebastian. He saw Sebastian trademark smirk cross his face. "Well Young Master, I was thinking we enlist Undertaker. Get him to masquerade as one of the leaders of the drug dens Her Majesty wants us to dispose of, kill the humans, attract the Reapers, and then take it from there, eh? And plus, I want to teach you how to spit bullets like I do. That would be fun." Sebastian joked. "Great idea Sebastian. Now all we need to do is get Undertaker involved. Let's go pay him a little visit, shall we?" Ciel turned and strode off briskly in the direction of the Undertaker's funeral parlor.

"Undertaker, I need to talk to you. I need your help." Ciel glanced round the supposedly empty shop. "Undertaker? Dammit, where are you, you stupid Shinigami!" "Right here My Lord, no need to yell. I don't see your butler anywhere." The Undertaker complained as he stepped out of a nearby coffin. Ciel gasped, his eyes briefly flashing red in surprise. "Why, Young Earl, I thought you were human. Oh well. What do you need. You know my price. Give me the gift of true laughter, and all my help is at your disposal." "I have no jokes for you Undertaker, but I have a proposal. If you give me the help I need, it'll be well worth the trouble." The Undertaker stared at him quizzically, his luminescent green eyes shining in the dim light. "What do you want me to do?" He asked the boy. Ciel explained their plan and the Undertaker laughed hysterically. "My Young Earl, that is a GREAT idea. Have you kidnapped the head of the drug den." The Undertaker checked. Suddenly Sebastian walked in, holding an injured man by the shirt. "Here you go, Undertaker. Can you mimic his appearance?" Sebastian checked. The Undertaker's outline suddenly blurred, his hair shortening and turning mousy brown, his eyes obscured by glasses, a jagged scar running down one cheek. Ciel stared, absolutely gobsmacked. He was identical to the man in Sebastian's arms. "I will be going now." And the Undertaker walked off. Ciel stared blankly at him for a moment before coming to his senses. "Let's go Sebastian. Time to have some fun." He turned and strode away, his cloak flapping in the wind. Sebastian drew himself into his usual elegant pose. "Yes, My Lord."


	2. Chapter 2

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 **Disclaimer: I waited so long to update because I was hoping I could tell you I was Yana Toboso... It didn't work!  
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With their demonic advantages, Ciel and Sebastian literally managed to walk straight through the front door of the drug den. In fact, they were first noticed on the far side of the warehouse, where a watchman spotted the well-dressed pair and raised the alarm, perhaps believing that the nobly attired gentlemen were leading some form of police entourage. "Sebastian, this is an order. Do not worry about me, kill the men in the back, and take Undertaker 'hostage.' Ciel explained it was merely to help attract the Reapers." Ciel ordered the demon. Sebastian glanced around at the ring of men now surrounding the pair, before dropping to one knee and bowing deeply. He smirked "Yes, My Young Lord." When he stood, gunshots rang out across the room. Instinctively the butler leaped in front of the young boy, a shield from the hail of bullets raining down upon them. Suddenly, a bullet tore through the base of the demon's spine, trailing scraps of torn fabric and ripped flesh. As if in slow motion, Ciel watched the bullet travel through the air and bury itself in his heart.

It felt as if a flame was passing through his chest. Never, in all of his fourteen years, had he ever felt such agony. He clenched his jaw. _I will not scream,_ Ciel thought stubbornly. Suddenly, Sebastian lurched to the side, running through a small exit after several gunmen, leaving Ciel vulnerable. Another entourage of bullets ripped through his body, and Ciel was just about to yell himself hoarse with pain before a bullet lodged itself in the back of his throat, aptly cutting off any chance of him screaming. He hit the ground, and through the haze of agony, he felt himself slip into unconsciousness.

When he came to, Ciel had one HELL of a headache. He scanned the room for Sebastian, but judging by the carnage, he had already dispatched most of the men in the area and had moved on. Ciel rose slowly to his feet, stretching his muscles, groaning as bullets scraped against every muscle and bone. He heard yells as the few men still alive gasped in shock when he stood and dusted himself off. He wandered calmly over to the nearest body and knelt beside it. He could sense the man's soul still residing inside his body. Instinctively, he pressed his lips to the corpse and felt a strange pulsating throughout his very being, resonating in his very core. He felt unimaginable strength wash over him, and he gasped as the divine taste hit his tongue. It tasted divine, the best thing ever to pass his lips. He straightened and looked at the men. He was unstoppable. He could take them all. _And I will devour the souls of every last one,_ He thought sardonically. Then he whirled into action.

Sebastian found his master greedily consuming the souls of the men he had killed. His eyes widened in shock at the massacre before him. Ciel had pulled the men to pieces, strangling and disemboweling them with a complete lack of elegance. He was soul mad! Instantly, Sebastian pinned him against the wall and slapped him across the face. Ciel blinked confusedly before coming to his senses. "Se-Sebastian?" He muttered weakly. Sebastian gently tied his eye patch back round his young master's head. Sebastian whipped his head up. He could hear voices..."Reapers. Brace yourself My Young Master." Sebastian warned. Ciel didn't reply. Suddenly, three Shinigami burst into the room. A pruning pole, a lawnmower and a chainsaw shot in the direction of the pair. Sebastian yanked Ciel out of the way and was impaled through the chest. He laughed as he pulled off the chainsaw stuck between his ribs. The Reapers who wielded it pulled back in shock. "You can't harm me!" Sebastian explained confidently. The William T. Spears, Grell Sutcliffe and Ronald Know stared back at him blankly. Sebastian strode over to Ciel, who was gasping and coughing blood. "My Young Lord, listen to me. Tense your stomach muscles, then visualize spitting the bullets to the ground." The butler instructed. Ciel tried to do what he was told, and soon was hacking multitudes of bullets to the floor. The Shinigami stared. "Impossible. The Phantomhive boy is human, yet he has the power of a demon. How can that be?" Grell inquired, awestruck. Sebastian didn't answer, instead engaging him in battle once more, the deadliest dance ever performed. The Reapers looked confused as to why their Death Scythes were not causing the demon any harm. Williams eyes glinted, and he leaped forward, plunging his Death Scythe to the hilt in Ciel's chest. The boy shook it off, his eyes glowing red. And so the battle resumed. All night the Shinigami and the demons fought, neither gaining the upper hand on the other. Hours later, the clock stuck midnight, and in that split second, Grell buried his chainsaw deep in Ciel's stomach. At that same moment, Ciel screamed, his blood red eyes turning his usual cerulean blue. He stared unseeingly at Sebastian, whose heart dropped into his chest. Blood trickled from the corner of Ciel's mouth before he collapsed, his cinematic record unfurling. "MASTER!" Sebastian screamed. He felt scared, his young master was dying...wait, why did he care? He was just a human after all, even if his soul was divine. So why did he care so much? Sebastian didn't care; he just wanted his Master to be okay. He watched as the Reapers began surveying his Cinematic record, when Ciel began to cough, blood gurgling from his throat. "My Young Lord!" Sebastian yelled once more, hoping beyond hope that Ciel would be okay. Alas, life was never that easy, and Fate never that kind.


	3. Chapter 3

**Hi again, wonderful readers!**

 **Thank you for all the great support you guys are showing me. Special thanks to Koalaboo92 for reviewing and critiquing, I really appreciate it!**

 **Disclaimer: I was going over the profit I've made from Kuroshitsuji the other day, and had a grand total of nothing... but that's OK, I have a pretty dope cactus, so I'm fine!**

 **Thanks again for reviewing. On with the story!**

Sebastian leaped to his Master's side and snatched him into his arms, jumping back from the Reapers as they attempted to cleave him in two with their Death Scythes. "Sorry, but I believe Ciel Phantomhive belongs to me." Sebastian called to them pleasantly, his eyes briefly flashing demonic red in annoyance. "See, that's where you're wrong, Bassy dearest. We Reaped him so his soul belongs to us. Isn't it obvious?" Grell purred. Sebastian straightened and looked the Shinigami in the eye. He clearly, carefully stated, so that the Reapers wouldn't miss a word, "I disagree."

Sebastian eyes seemed to flash a strange, eerie blue for a moment before he continued. "Therefore, I charge you with stealing a soul promised to a demon. You are now to go on trial at the Supernatural High Court. This I rule with the power I possess." The trio of Death Gods gasped. "You cannot do that!" William T. Spears complained. "Only God and the Archangels can order such a summoning, as you know well, you filthy Demon!" Sebastian smirked. "Why don't you ask God himself then," pointing out the warehouse window. Suddenly the window shattered, and through the rain of glass, a figure robed in white flew into the storeroom. The Reapers stared, then fell to their faces and grovelled. "God, My Lord, what are you here for? How can we help, Sir?" The Shinigami inquired. "I am replying to a court summons. I need to bind the defendants to the rules of the court. I will bind you with the angelic rune." The Death Gods stared. God approached them with a seraph blade, apparently ready to carry out his statement. William suddenly found his voice. "Lord, you cannot be taking the orders of this vermin." He spat. "Only an Archangel can order a trial." He elaborated. God stared strangely at him for a moment before continuing. "See, little Reaper, that is where you are wrong. This demon does indeed have the right to order such a trial. All shall be explained in time, but first I need to bind you to the court terms with a rune. Are you amenable to the conditions? Remember, if you disagree with the terms and refuse to have your arm marked, the opposition win the trial by default. So what shall it be." God asked imperiously.

The Shinigami shared a look between them before sighing and holding out their forearms. "We agree to the terms of the trial, and we agree to be held to our word through the binding rune of the Angelic Covenant." They announced in unison. God smirked, a smile that would have been at home on Sebastian's face, and walked up to the Death Gods, bringing the seraph blade down on the inside of the first Reaper's wrist, inscribing a deep rune that looked like an A, but with the ends curving upwards before dropping down again in a swirling spiral. It glowed red before fading to an inky black. God repeated it with the next two Shinigami. "Now that that's over with, let's get to Heaven to begin the trial." Ronald Knox instructed. God seemed slightly confused, unsure of what he meant perhaps. Then his grin widened, and he held up the seraph blade before continuing "You, forget, I have still not bound the trial's instigator. Sebastian Michaelis, Raven Demon of Hell, come forward and be bound." The Reapers stared in shock. "But, Lord, binding a demon with an angelic rune will kill my darling Bassy!" Grell complained. The Lord shot him a strange look. "Stupid Reaper... Michaelis will certainly survive the Binding. Let him be bound." The Shinigami stepped backwards, allowing Sebastian to walk up to God. He bared his arm and let the seraph blade dig deeply into his arm. Upon his wrist was the same symbol adorning the Shinigamis' skins, but his mark faded from blood red to pure white, and the Reapers wondered at it but said nothing. "Right, now that's over with, let's go to Heaven... Michaelis, are you okay? Michaelis?" Sebastian seemed a bit unfocused, and his eyes shone strangely. "Oh, yes Lord, I'm fine. Let's go to Heaven." God looked at him severely before continuing, explaining "Michaelis... can you please open the Heavenly Gateway for me?" Sebastian's eyes widened, and he smiled, an actual, genuine smile, as if he was truly happy for once. "...Me, Lord. Really? I - I can't - I mean - Thanks." He stuttered. The Shinigami looked on in confusion and outrage. Firstly, Sebastian NEVER stuttered. Also, since when could a DEMON open the Heavenly Gateway. Grell raised his voice in protest, "Sir, not to seem rude, but NO Demon, even if it is my darling Bassy, has the right to open the gateway to Heaven, especially not over a trained Reaper like the three of us. Please pick one of us instead. Bassy here isn't even able to do such a thing, he does not possess the Heavenly Power need to open the Gateway!" He finished with a yell. God's eyebrow twitched in annoyance before he replied. "As I mentioned earlier, Michaelis does indeed have the power to open the Gateway, and I will not take no for an answer. Now, Michaelis, **open the gateway.** " Sebastian stepped forwards, holding up his hands as he began chanting in a strange language foreign to the Shinigami. The room began to glow with a harsh white light, and suddenly there was a supersonic BOOM, and the warehouse was empty.

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 **Sorry if Sebastian is a little OOC, I'm trying my hardest to keep him reasonably in character, but a bit kinder and more susceptible to emotions. I hope you enjoyed! Next chapter will be up soon.**


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